This invention is directed to a shelter construction having appropriate panels and panel joints to provide thermal and structural integrity of the shelter to provide protection of contents in severe environmental conditions.
Shelters of various sorts have been built since the earliest beings on earth evidenced intelligence. The particular shelters of this invention are related to modern high performance concepts. Attention has been given to modular methods of containerization of equipment. While such as useful in military circumstances, it is also useful for other, non-millitary ends, where equipment protection is desired, together with mobility. Such situation is found at construction sites, particularly sites of heavy construction such as bridges, dams, highways, office buildings, and in oilfield use. The advantage of the modular technique is the relative ease with which equipment enclosed in such a shelter can be transported and deployed. As used with respect to this invention, the term "Shelter" refers to a special type of container which can be used to house equipment of electrical nature, or other types, and is large enough so that the equipment enclosed can be operated by technicians without removing the equipment from a shelter. Additionally, the shelter is weatherproof construction, since it may be deployed under extreme environmental conditions. While the shelter is expected to permanently house equipment under such conditions, it should be noted that the term "shelter" is applied to the housing rather than the combination, and furthermore, the shelter may be employed only to protect the equipment during transportation in cases where the equipment is subsequently unloaded.
Several manufacturers build shelters, and various panel constructions have been employed, but none of the shelters or panel constructions have been as advantageous as those described with respect to this invention. Previous panel constructions of sandwich construction have been the most successful. This prior construction consists of two relatively thin, high density, high strength facings bonded on opposite sides of a relatively thick, low density, low strength core. The facings carry the load in the plane of the panel, while the core carries shear stresses and resist compression loads normal to the plane of the panel. Aluminum facings of various thicknesses are generally employed. Paper honeycomb, polymer composition foam with or without reinforcement therein, plywood, and aluminum honeycomb have been used as core materials. However, each of these by itself has disadvantages when all environmental, weight and loading problems are considered. The principal shelter requirements which advise against the use of the above-listed core materials are the requirement of being moisture-proof, having adequate thermal insulation, having capacity for random insert installations and the weight limits imposed upon the finished shelters. The paper honeycomb provides high strength-to-weight ratio, but it cannot meet the moisture-proof requirements. Polymer composition foam alone is a thermal insulator of adequate value, but it has inadequate strength for random insert installation. Polymer composition foam with strengthening beams lying on edge therein satisfies the thermal and strength requirements, but is usually too heavy, is expensive to construct, and has no capacity for random insert installation. Plywood alone is too heavy. An aluminum honeycomb core does not satisfy the thermal requirements.
Once a panel of adequate thermal and structural properties has been achieved, it is also necessary to provide a means for joining two panels and/or terminating a panel edge. To accomplish this, closeouts and joints between panels must be provided. Flexible or semi-rigid joints charcterize the shelter assemblies of the prior art, with cost and ease of assembly being cited as the primary reasons for the flexible joint. It has also been argued that a flexibly-joined structure will be subjected to lower acceleration levels during shock loading. However, the primary failure of shelters is the leakage of moisture. This leakage is often the result of joint failure which has resulted from panel movement. The flexible joint construction used by several manfacturers consists of a thin-walled extrusion tee, or channel-angle combination fastened in some manner to attach intersecting panels. Several of this type, applicable to sandwich construction panels, are described in U.S. Pat. No. 2,986,245.